Browsing Earth and Environmental Systems by Subject "Geochemistry."
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Applying Geophysics and Geochemistry to Understand Middle Woodland Site Spatial Organization At the Northwood Site, Vigo County, IndianaThe Northwood site (12Vi194) in northern Vigo County is attributed to the Late Middle Woodland culture known as Allison-LaMotte. Previous studies at other Allison-LaMotte sites are inconclusive regarding the village structure of this culture. While some studies identify a habitation zone surrounding a circular plaza, other Allison-LaMotte sites lack an observable spatial layout to the site. Magnetometry studies completed at the Northwood site in 2005 reveal a possible semi-circular community pattern with a central plaza. This study employed the 2005 magnetometer survey data, magnetic susceptibility, ground penetrating radar (GPR), and geochemical analyses to confirm the hypothesized site organization. Magnetic data from the magnetometer survey and magnetic susceptibility of artifact classes were compared to identify sources of magnetic anomalies. The map produced by magnetometry was compared with the GPR map to identify overlaps in possible pit features and the plaza zone. Excavating in locations identified as magnetic anomalies allowed for ground truthing survey results and collecting magnetic susceptibility measurements and soil samples for geochemical analysis. Geochemical analyses included detailed phosphorus geochemistry, total organic matter content, and organic carbon enhancement of soils collected from the site. Finally, determination of the source and strength of feature magnetic signals were analyzed using magnetic susceptibility and magnetometer data. These investigations provide better estimates of site spatial structure at the Northwood Site.
Assessing Environmental Conditions at the Friar Tuck Mining Complex, Dugger, IndianaMany abandoned mine lands (AML) continue to present significant environmental concerns. The abandoned Friar Tuck Mining Complex in Greene and Sullivan counties, Indiana, continues to impair local water quality despite closing in 1952 for operations and multiple remediation attempts. Most areas within the Friar Tuck Mining Complex have been successfully remediated; however, the area of research interest requires additional treatment and continues to be impacted by runoff from gob piles. Subsequently, areas characterized by a loss of vegetation where mine seeps occur behave unpredictably and are characterized by the exposure of bare soil. These mine seep areas are of particular concern because contaminated soil may leave the site during summer months as aerosols due to soil desiccation. The primary goal of this project was to evaluate spatial variability in the distribution of metals in surface soils. In May 2010, 258 soil samples were collected at the Friar Tuck Mining Complex to evaluate metal accumulation and bioavailability using several different geochemical techniques, including bulk geochemistry following reaction with water and acid and a sequential extraction technique. Results indicate that surface soils at the Friar Tuck Mining Complex continue to be degraded, pH is moderately to highly acid (pH=4-1) in areas of mine seeps, surface flow, and where the slurry pond narrows and begins to discharge into Mud creek. Surface soils also have elevated concentrations of bioavailable metals due to the persistent influence of AMD, such as Zn, Cu, Cr and Pb, especially in areas of mine seeps, surface flow, and water ponding.
Comparisons of Distributions and Isotopic Geochemistry of Benthic Foraminifera from Seep and Non-seep Environments, Offshore of Costa RicaVertical distribution patterns and stable isotopic geochemistry of benthic foraminifera labeled with CellTracker Green and stained with Rose Bengal were compared at sites of active methane seepage and adjacent non-seep habitats off the Pacific coast of Costa Rica. Sediment cores of bacterial mats from Costa Rica revealed vertical distribution patterns more similar to those seen previously in clam beds, suggesting increased levels of bioturbation compared to nonseep sites. Similar taxa were found at both seep and non-seep sites including: Chilostomella oolina, Uvigerina peregrina and hispida, Cibicides mckannai, and Cassidulina braziliensis. Within active methane seep habitats, elevated substrate such as carbonate rocks, and vestimentiferan tubeworms were examined for living foraminifera. Vestimentiferan tubeworms had highly variable numbers of attached epibenthic foraminifera, dominated by Cibicides wuellerstorfi and Carpenteria monticularis. Stable carbon isotopic comparisons between epibenthic foraminiferal species of Cibicides wuellerstorfi and the vestimentiferan tubeworms on which they reside revealed 10‰ to 30‰ differences between the foraminiferal carbonate and substrate, suggesting that the geochemical signatures of elevated epibenthics were not significantly influenced by the geochemical signature of the substrate on which they reside. This study finds no apparent methane influence on the foraminiferal calcite of elevated epibenthic foraminifera from the three active seep sites studied (Mound 11, Mound 12, and Jaco Scar). This may be because the elevated epibenthics were not exposed to seep-influenced fluids by inhabiting raised substrates. This study also provides a quantitative analysis of coiling directions in elevated epibenthic species at seeps, which has never previously been reported. Statistical analysis revealed that there were no significant differences in isotopic composition between sinstral (left)and dextral (right) coiling Cibicides wuellerstorfi. The results of this study suggest that coiling direction of elevated epibenthic oraminifera, such as Cibicides wuellerstorfi and Carpenteriamonticularis, is a result of biologic factors rather than environmental influences.
Glacial/Interglacial Export Production in the Subantarctic South PacificAtmospheric CO2 varied considerably in the past; however, the mechanisms that drive this variability are poorly understood. CO2 is linked to marine primary productivity through the biological carbon pump (BCP), leading to hypotheses that past increases in BCP efficiency in areas such as the Southern Ocean may have contributed to glacial CO2 drawdown (Sarmiento & Toggweiler, 1984). Productivity has varied considerably in the past, but the extent, timing, and impacts remain poorly understood. The Subantarctic South Pacific is an area of the ocean that is crucial to the understanding of both glacial climate and paleo-export productivity. Unfortunately, few studies have investigated the central South Pacific because it is so remote. The sediment core MV0502-04JC was recovered from the Subantarctic South Pacific in February-March 2005 at 50°S. The results of this study will be compared with data from ODP Leg 189, Site 1171, also in the Subantarctic South Pacific. Data from these cores will be used to evaluate glacial/interglacial paleo-export production and terrigenous provenance using bulk sediment geochemical proxies, including detailed P geochemistry, P, Ba, and metal elemental ratios, and Baxs. The results of this research suggest each site has variable terrigenous provenance that may have relatively different Fe content. Export production at MV0502-4JC is invariant down core; however, Site 1171 does exhibit glacial/interglacial variations in export production.